Electrical power lines pose a serious crash hazard to helicopters and other air-based vehicles, especially small aerial vehicles, such as unmanned aerial vehicles (UAVs). This is because power lines are so widespread, hard to see, and strung at roughly the same height above the ground that these aircraft fly. In fact, according to one report by the Federal Aviation Administration (FAA), power lines are the cause of roughly 5% of helicopter accidents. This statistic applies to both civilian and military cases. Another report found power-line collisions are responsible for 31% of accidents among agricultural aircraft. In many of these accidents, there were fatalities and injuries.
Current active systems for seeking to identify power lines, such as radar- or laser-based ones, are bulky, expensive, energy inefficient, and they generate unwanted signatures that could compromise their mission. Simple methods that use only passive electric- or magnetic-field sensors can easily fail when used near three-phase power lines. Moreover, these simple methods do not provide information on the orientation of the lines, the direction of power flow, or otherwise help UAVs avoid power lines.